CN113877605A

CN113877605A - A kind of catalyst for low temperature oxidation of CO and preparation method thereof

Info

Publication number: CN113877605A
Application number: CN202110178373.8A
Authority: CN
Inventors: 脱永笑; 冯翔; 曹建琳; 张晓倩; 孟营; 闫昊; 周鑫; 刘熠斌; 杨朝合; 陈德
Original assignee: China University of Petroleum East China
Current assignee: China University of Petroleum East China
Priority date: 2021-02-09
Filing date: 2021-02-09
Publication date: 2022-01-04
Anticipated expiration: 2041-02-09
Also published as: CN113877605B

Abstract

一种低温氧化CO的催化剂及其制备方法，该催化剂包括，以Pt元素为活性组分、过渡金属元素M2氧化物和碱金属元素M1组成，M2选自Mn、Mo、Fe、Ni元素的一种或者几种，M1为碱金属元素，其中，Pt元素占所述催化剂总质量百分比为0.1‑2wt％，M1元素占催化剂总质量的1‑10wt％。首先以M1OH或M1₂CO₃为沉淀剂通过共沉淀法制备Pt‑M1‑M2的碱式混合物，然后通过高温处理制备出Pt/M1‑M2催化剂。该催化剂在多种特性气氛(如富氢、富二氧化碳、含硫)中具有较高的CO催化氧化活性和稳定性，在燃料电池、汽车尾气和低温甲醇洗尾气等CO消除场景中具有良好的应用潜力。A catalyst for oxidizing CO at low temperature and a preparation method thereof, the catalyst comprises, using Pt element as an active component, a transition metal element M2 oxide and an alkali metal element M1, M2 is selected from one of Mn, Mo, Fe, and Ni elements. One or more kinds, M1 is an alkali metal element, wherein, the percentage of Pt element in the total mass of the catalyst is 0.1-2wt%, and the element M1 is 1-10wt% in the total mass of the catalyst. Firstly, the basic mixture of Pt-M1-M2 was prepared by co-precipitation method using M1OH or M1 ₂ CO ₃ as precipitant, and then the Pt/M1-M2 catalyst was prepared by high temperature treatment. The catalyst has high CO catalytic oxidation activity and stability in various characteristic atmospheres (such as hydrogen-rich, carbon dioxide-rich, sulfur-containing), and has good performance in CO elimination scenarios such as fuel cells, automobile exhaust and low-temperature methanol wash exhaust. application potential.

Description

Catalyst for oxidizing CO at low temperature and preparation method thereof

Technical Field

The invention relates to a catalyst for CO oxidation, in particular to a catalyst for CO oxidation in a plurality of characteristic atmospheres (such as hydrogen-rich atmosphere, carbon dioxide-rich atmosphere and sulfur-containing atmosphere).

Background

CO is one of main atmospheric pollutants, is easily combined with hemoglobin of a human body and is not easy to separate, so that oxygen deficiency of organism tissues is caused, even the human body is suffocated to die, and a male human body has a poisoning symptom within 1 hour when the concentration of CO in the air reaches 650 ppm. Meanwhile, in the petrochemical industry, catalysts used in many chemical processes have extremely high sensitivity to CO, and trace amounts of CO can poison or deactivate the catalysts. Therefore, effective elimination of CO has important applications in many areas, such as automobile exhaust gas purification, elimination of CO from industrial exhaust gas, and purification of hydrogen for fuel cells.

The CO catalytic oxidation is an effective method for eliminating CO, and has the advantages of simple process, economy, high efficiency and the like. In practical applications, the reaction gas usually contains a plurality of other gases besides a small amount of CO, and the types of the gases are different according to different application scenes, and the gases may seriously affect the catalytic oxidation performance of CO of the catalyst. For example, in proton exchange membrane fuel cells for CO removal under hydrogen-rich atmospheres, during CO adsorption oxidation, H₂Will compete for adsorption on the catalyst surface and O₂A reaction occurs, resulting in a decrease in catalytic oxidation activity and selectivity of CO. In the low-temperature methanol washing tail gas CO removal and CO2 laser gas purification, the reaction gas is rich in CO₂Atmosphere, CO₂Will be catalyzedCarbonate species are generated on the surface of the catalyst, so that active sites are blocked, the CO oxidation reaction is hindered, and the activity and the stability of the catalyst are greatly influenced. In addition, the realization of efficient CO removal at low temperature can reduce energy loss and economic investment.

The present application is made in view of the above problems.

Disclosure of Invention

It is an object of the present invention to provide a catalyst for CO oxidation, which has high catalytic CO oxidation activity and stability in various characteristic atmospheres (such as hydrogen-rich, carbon dioxide-rich or/and sulfur-containing).

It is another object of the present invention to provide a catalyst for CO oxidation, which has high activity and stability for low-temperature catalytic oxidation of CO in various characteristic atmospheres (such as rich hydrogen, and/or rich carbon dioxide).

The invention also aims to provide a preparation method of the catalyst for CO oxidation, which is simple and the obtained catalyst has higher CO catalytic oxidation activity and stability.

To achieve the object of the present invention, a catalyst for CO oxidation comprises: pt element is used as an active component, transition metal element M2 oxide and alkali metal element M1, M2 is selected from one or more of Mn, Mo, Fe and Ni elements, M1 is alkali metal element, wherein Pt element accounts for 0.1-2% of the total mass of the catalyst, and M1 element accounts for 1-10 wt% of the total mass of the catalyst.

A preparation method of a catalyst for CO oxidation comprises the steps of mixing a Pt precursor solution and an M2 precursor solution to obtain a mixture A, dropwise adding the mixture A into a solution containing an M1 element, adjusting the pH value to 7-10 after dropwise adding is finished to obtain a mixture B, and crystallizing, washing and performing high-temperature treatment on the mixture B to obtain the catalyst.

The catalyst for CO oxidation in the application preferentially oxidizes CO in various atmospheres (such as hydrogen-rich atmosphere, carbon dioxide-rich atmosphere and sulfur-containing atmosphere), and shows excellent CO catalytic oxidation activity and stability. Therefore, the catalyst can be applied to CO elimination scenes such as fuel cells, automobile exhaust, low-temperature methanol washing exhaust and the like.

Drawings

FIG. 1 is a graphical representation of the stability performance of a CO oxidation catalyst of the present application.

Detailed Description

The catalyst for CO oxidation of the present invention is described in further detail below. And do not limit the scope of the present application, which is defined by the claims. Certain disclosed specific details provide a thorough understanding of various disclosed embodiments. One skilled in the relevant art will recognize, however, that embodiments may be practiced without one or more of the specific details, with other materials, etc.

Unless the context requires otherwise, in the description and claims, the terms "comprise," comprises, "and" comprising "are to be construed in an open-ended, inclusive sense, i.e., as" including, but not limited to.

Reference in the specification to "an embodiment," "another embodiment," or "certain embodiments," etc., means that a particular described feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, "an embodiment," "another embodiment," or "certain embodiments" do not necessarily all refer to the same embodiments. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Each feature disclosed in this specification may be replaced by an alternative feature serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, the features disclosed are merely generic examples of equivalent or similar features.

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers. All percentages, ratios, proportions, or parts are by weight unless otherwise specified.

The weight volume percentage units in the present invention are well known to those skilled in the art and refer to, for example, the weight of solute in a 100ml solution.

In the present invention, the concentration unit "M" of the solution means mol/L.

The term "crystallization" is the process by which a substance crystallizes in a chemical reaction.

The term "aging" is the natural settling of the catalyst structure towards stability.

In the present application, the metal oxide in the catalyst is calculated as the oxide corresponding to the highest valence state of the metal element.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention. The preferred embodiments and materials described herein are intended to be exemplary only.

The application mainly aims at the defects that other impurity gases existing in CO catalytic oxidation seriously affect the CO catalytic oxidation performance of the catalyst (such as selectivity reduction, catalyst poisoning inactivation and the like) in practical application, and provides the CO oxidation catalyst with high activity and stability in various characteristic atmospheres (such as hydrogen-rich atmosphere, carbon dioxide-rich atmosphere and sulfur-containing atmosphere) and the preparation method thereof.

In one aspect, a catalyst for CO oxidation, comprising: pt element is used as an active component, transition metal element M2 oxide and alkali metal element M1, M2 is selected from one or more of Mn, Mo, Fe and Ni elements, M1 is selected from Na and/or K elements, wherein the Pt element accounts for 0.1-2 wt% of the total mass percent of the catalyst.

The mass of the M1 element is 1-10 wt% of the total mass of the catalyst; preferably, the mass of M1 is 2-5 wt% of the total mass of the catalyst.

The remaining amount in the catalyst was the content of substances containing various forms of the transition element M2.

In certain embodiments, M2 is selected from one or more of the elements Mn, Fe and Ni, and the mass of the element Pt is 0.15-3% of the mass of the oxide M2.

In the catalyst for CO oxidation of the present application, an excess amount is introducedAlkali metal element to construct highly effective Pt inside the catalyst⁺—O(OH)_xM1 and Pt⁺—O(OH)_xThe M2 synergistic interface can optimize the adsorption capacity of CO on the active center and promote the activation of oxygen, thereby obviously improving the catalytic oxidation performance of CO, and simultaneously, the synergistic interface promotes H₂、H₂And the fast migration of S and other oxidation products prevents the blockage and poisoning of Pt active centers. Therefore, the catalyst shows excellent CO catalytic oxidation activity and stability in various characteristic atmospheres (such as rich hydrogen, rich carbon dioxide and sulfur); the catalyst shows excellent CO low-temperature catalytic oxidation activity and stability in various characteristic atmospheres (such as rich hydrogen and rich carbon dioxide). In particular the mass of the M1 element is 1 to 10 wt.% of the total mass of the catalyst; preferably, the mass of M1 is 2-5 wt% of the total mass of the catalyst, and the catalyst shows better CO catalytic oxidation activity and stability in various characteristic atmospheres (such as hydrogen-rich atmosphere, carbon dioxide-rich atmosphere and sulfur-containing atmosphere).

In certain embodiments, the transition metal element M2 is an Mn element.

Catalysts containing Mn, Pt and an alkali metal element, which are gases (such as hydrogen sulfide) generally contained in industrial process gases in a complicated atmosphere, particularly in the case where the gas mixture to be treated also contains elemental sulfur, have excellent catalytic oxidation performance with respect to CO in the gas mixture.

The catalyst can be suitable for reaction processes such as adiabatic, self-heating, heat exchange and heat accumulation fixed beds.

On the other hand, the above catalyst for CO oxidation is prepared by a coprecipitation method.

In the application, especially the CO oxidation catalyst prepared by a coprecipitation method, more alkali metal elements can be introduced, and the mass of the M1 element is 1-10 wt% of the total mass of the catalyst; preferably, the mass of M1 is 2-5 wt% of the total mass of the catalyst. Construction of highly efficient Pt in catalyst internal structure⁺—O(OH)_xM1 and Pt⁺—O(OH)_xM2 synergistic interface, and further, exhibits excellent CO catalytic oxygen in a variety of characteristic atmospheres (e.g., hydrogen rich, carbon dioxide rich, sulfur containing)Chemical activity and stability; the catalyst shows excellent CO low-temperature catalytic oxidation activity and stability in the atmosphere rich in hydrogen and/or carbon dioxide.

A preparation method of a catalyst for CO oxidation comprises the steps of mixing a Pt precursor solution and an M2 precursor solution to obtain a mixed solution A, dropwise adding the mixed solution A into a solution containing an M1 element, adjusting the pH value to 7-10 after dropwise adding is finished to obtain a mixture B, and crystallizing, washing and performing high-temperature treatment on the mixture B to obtain the catalyst.

In one embodiment, the Pt precursor is a water-soluble platinum element-containing salt solution. Preferably, chloroplatinic acid or platinum chloride is included.

The precursor M2 is water-soluble salt solution containing M2 element. Preferably nitrate or chloride salts containing the element M2.

The solution containing M1 element comprises M1OH or M1₂CO₃。

In the application, the oxide or hydroxide of the transition metal M2 can form strong interaction with Pt, so that the Pt shows high dispersibility, the stability of the high-dispersion Pt is enhanced by the introduction of alkali metal, and the preparation method is simpler and is easy to prepare on a large scale.

In one embodiment, the ratio of the amount of species of element M1 in the solution of element M1 to the sum of the amount of species of Pt in the Pt precursor solution and the amount of species of M2 in the M2 precursor solution is 2: 1-4: 1.

the mass of the Pt element is 0.15-3% of that of the M2 oxide.

In certain embodiments, the concentration of the Pt precursor may be 0.05M to 0.1M, and the concentration of the M2 precursor is 0.5M to 1.5M.

The concentration of the solution containing M1 element was 0.1M to 0.5M.

Depending on the amount of treatment in practice, the concentration of the precursors of the respective elements can be adjusted accordingly.

The solution for adjusting the pH of the solution is a dilute acid solution, such as dilute hydrochloric acid or dilute nitric acid.

The temperature of the mixture A and the solution containing the M1 element is 50-90 ℃.

In certain embodiments, a drying step is performed prior to the high temperature treatment, the drying temperature being less than 100 ℃.

In some embodiments, the high temperature treatment is heating at a temperature of 150 ℃ and 400 ℃. The high-temperature treatment process is carried out in an air atmosphere or in a mixed gas containing hydrogen.

Alternatively, the high-temperature treatment is performed in an air atmosphere and then in a mixed gas containing hydrogen.

The hydrogen-containing mixed gas may further include an inert gas such as argon or helium.

In some embodiments, the hydrogen-containing gas mixture contains about 10% hydrogen by volume.

The mixed gas containing hydrogen is continuously introduced into the heating environment, and the flow rate is generally about 50 mL/min.

The content of hydrogen in the mixed gas and the flow rate of introduction of the mixed gas can be adjusted according to the amount of the catalyst to be specifically treated.

In the application, the high-temperature treatment is carried out at the temperature of 150-400 ℃, and the proportion of valence Pt and metal Pt can be controllably constructed by introducing air or/and mixed gas containing hydrogen. Thus, CO and H can be optimized₂、CO₂、H₂The adsorption energy of gases such as S on Pt active centers realizes preferential oxidation of CO in an atmosphere in which a plurality of impurities are mixed.

In some embodiments, the high temperature treatment is heating at a temperature of 150 ℃ and 250 ℃.

Preferably, the temperature of the high-temperature treatment is 150-400 ℃, and the time of the high-temperature treatment is preferably 0.5-2 h.

In some embodiments, the dried solid material is subjected to heat treatment in an air atmosphere at a temperature range of 150-400 ℃, and then subjected to heat treatment in a hydrogen-containing mixed gas, so that the obtained catalyst has good oxidation catalytic performance on CO in an atmosphere rich in hydrogen, carbon dioxide and the like, and the conversion rate of CO can reach more than 90% and even up to 99% under a low-temperature (even lower than 80 ℃) reaction condition.

Further, the preparation method of the catalyst for CO oxidation specifically comprises the following steps:

and dissolving a proper amount of Pt precursor solution in the M2 precursor solution, and uniformly stirring to obtain a mixed solution A.

Dropping the mixed solution A into M1OH or M1 at 50-90 deg.C₂CO₃In the solution, after the dropwise addition is finished, adjusting the pH value to 7-10, crystallizing at the temperature of 50-90 ℃, and then standing at the temperature of 50-90 ℃ to obtain a precipitate;

washing the precipitate until no chloride ion exists in the washing liquid, drying the washed precipitate in an oven, and finally performing high-temperature treatment at the temperature of 150 ℃ and 400 ℃ to obtain the catalyst.

In some embodiments, the crystallization time is preferably from 2h to 4 h.

The standing aging time is preferably 1h-5 h.

The conditions of the high temperature treatment are as described above and will not be described in detail.

In another aspect, the catalyst for CO oxidation is prepared by a CO-impregnation method.

A preparation method of a catalyst for CO oxidation comprises the steps of mixing a Pt precursor solution with a solution containing M1 element to obtain a mixed solution B, dipping the mixed solution B on an oxide of M2, drying and carrying out high-temperature treatment to obtain the catalyst.

The kinds and amounts of the Pt precursor solution, the solution containing M1 element, and the oxide of M2 in the co-impregnation method may be the kinds and amounts of the corresponding substances in the above-described co-precipitation method.

The drying and high-temperature treatment can also adopt the process and process parameters of the coprecipitation method.

In a fourth aspect, the above-described CO oxidation catalyst is used by being coated on a honeycomb carrier. The specific method comprises the following steps:

mixing a Pt precursor solution, an M2 precursor solution and alumina powder to obtain a mixed solution A1, mixing a solution containing an M1 element with the mixed solution A1, adjusting the pH value to 7-10 to obtain a mixture B1, crystallizing, washing and drying the mixture B1 to obtain catalyst powder,

mixing the obtained catalyst powder, a surfactant and water to prepare catalyst slurry, mixing a ceramic carrier with a pore channel with the catalyst slurry to obtain a mixture C1, and performing high-temperature treatment on the mixture C1 to obtain the coating-type catalyst.

In certain embodiments, the surfactant is added in an amount of 0.5 to 8.0 wt% based on the weight of the catalyst powder.

The drying temperature is lower than 100 ℃. Drying until the water content of the catalyst is less than 5 wt%.

Preferably, the drying is carried out for 10h to 12h at a drying temperature of less than 100 ℃.

The surfactant includes but is not limited to one or a mixture of several of polyethylene glycol, glycerol, polyacrylic acid, cellulose ether and stearic acid.

The mass ratio of the surfactant to the water is 1:10-1: 80.

The ceramic carrier comprises cordierite honeycomb ceramic.

The coating on the ceramic support may be appropriately adjusted depending on the use environment. In the present application, the coating time is preferably 0.5h to 1.5 h.

In certain embodiments, the mass of Pt element is 0.5-2% of the mass of alumina.

The kinds and the amounts of the Pt precursor solution, the M2 precursor solution, and the M1 element solution can be referred to the kinds and the amounts of the corresponding substances of the above co-precipitation method.

The CO oxidation catalyst obtained by the method can achieve the effect even at a low temperature of below 100 ℃ when the conversion rate of CO is above 90% at a temperature of below 150 ℃ in a carbon dioxide-rich and/or hydrogen-rich atmosphere; the CO conversion rate reaches more than 99% below 185 ℃, and the effect can be achieved even at a low temperature below 100 ℃. In the atmosphere containing sulfur, the high-efficiency catalytic oxidation of CO can be realized, and the conversion rate can reach more than 99 percent.

The catalyst of the present invention and its catalytic effect are further illustrated below with reference to specific examples. The materials used in the following examples are all chemically pure standards. The catalysts prepared in examples 1-6 below had M1 contents between 2 and 5 wt%.

Example 1

0.53mL of a 0.07M chloroplatinic acid aqueous solution was dissolved in 14.0mL of a 1M ferric chloride solution, and the mixture was stirred uniformly to obtain a mixed solution A. Uniformly dripping the mixed solution A into 211.5mL of 0.2MKOH solution at the speed of 2mL/min under the condition of 80 ℃ water bath, adjusting the pH to 8.5 by using 1M HCl after finishing dripping, continuing stirring and crystallizing in the 80 ℃ water bath for 3 hours, and then standing and aging in the 80 ℃ water bath for 1 hour.

And centrifugally washing the obtained precipitate until no chloride ion exists in the washing liquid, then placing the precipitate in a drying oven for drying for 12 hours at the temperature of 80 ℃, and finally carrying out high-temperature treatment for 30min at the temperature of 200 ℃ in a hydrogen-argon mixed gas to obtain the 0.5% Pt/K-Fe catalyst.

Example 2

0.53mL of a 0.07M chloroplatinic acid aqueous solution was dissolved in 14.0mL of a 1M ferric chloride solution, and the mixture was stirred uniformly to obtain a mixed solution A. Uniformly dripping the mixed solution A into 212.3mL of 0.2M NaOH solution at the speed of 2mL/min under the condition of 80 ℃ water bath, adjusting the pH to 8.5 by using 1M HCl after finishing dripping, continuing stirring and crystallizing in the 80 ℃ water bath for 3 hours, and then standing and aging in the 80 ℃ water bath for 1 hour.

And centrifugally washing the obtained precipitate until no chloride ion exists in the washing liquid, then placing the precipitate in a drying oven for drying at the temperature of 80 ℃ for 12 hours, and finally carrying out high-temperature treatment in a hydrogen-argon mixed gas at the temperature of 200 ℃ for 30min to obtain the 0.5% Pt/Na-Fe catalyst.

Example 3

1.07mL of a 0.07M chloroplatinic acid aqueous solution was dissolved in 14.0mL of a 1M ferric nitrate solution, and the mixture was stirred uniformly to obtain a mixed solution A. Under the condition of 80 ℃ water bath, uniformly dripping the mixed solution A) into 212.3mL of 0.2M NaOH solution at the speed of 2mL/min, adjusting the pH to 8.5 by using 1M HCl after finishing dripping, continuing stirring and crystallizing in 80 ℃ water bath for 3h, and then standing and aging in 80 ℃ water bath for 1 h.

And centrifugally washing the obtained precipitate until no chloride ion exists in the washing liquid, then placing the precipitate in a drying oven for drying for 12 hours at the temperature of 80 ℃, and finally carrying out high-temperature treatment for 30min in hydrogen-argon mixed gas at the temperature of 200 ℃ to obtain the 1% Pt/Na-Fe-1 catalyst.

Example 4

1.07mL of a 0.07M chloroplatinic acid aqueous solution was dissolved in 14.0mL of a 1M ferric nitrate solution, and the mixture was stirred uniformly to obtain a mixed solution A. Uniformly dripping the mixed solution A into 212.3mL of 0.2M NaOH solution at the speed of 2mL/min under the condition of 80 ℃ water bath, adjusting the pH to 8.5 by using 1M HCl after finishing dripping, continuing stirring and crystallizing in the 80 ℃ water bath for 3 hours, and then standing and aging in the 80 ℃ water bath for 1 hour.

And centrifugally washing the obtained precipitate until no chloride ion exists in the washing liquid, then placing the precipitate in a drying oven for drying at the temperature of 80 ℃ for 12 hours, and finally carrying out high-temperature treatment in a hydrogen-argon mixed gas at the temperature of 400 ℃ for 30min to obtain the 1% Pt/Na-Fe-2 catalyst.

Example 5

And centrifugally washing the obtained precipitate until no chloride ion exists in the washing liquid, then placing the precipitate in a drying oven for drying for 12 hours at the temperature of 80 ℃, and finally respectively carrying out high-temperature treatment for 30 minutes at the temperature of 200 ℃ in the air and 30 minutes at the temperature of 200 ℃ in a hydrogen-argon mixed gas to obtain the 1% Pt/Na-Fe-3 catalyst.

Example 6

1.07mL of 0.07M chloroplatinic acid aqueous solution was dissolved in 14.0mL of 1M manganese nitrate solution, and the mixture was stirred well to obtain a mixed solution A. Uniformly dripping the mixed solution A into 212.3mL of 0.2M NaOH solution at the speed of 2mL/min under the condition of 80 ℃ water bath, adjusting the pH to 8.5 by using 1M HCl after finishing dripping, continuing stirring and crystallizing in the 80 ℃ water bath for 3 hours, and then standing and aging in the 80 ℃ water bath for 1 hour.

And centrifugally washing the obtained precipitate until no chloride ion exists in the washing liquid, then placing the precipitate in a drying oven for drying for 12 hours at the temperature of 80 ℃, and finally respectively carrying out high-temperature treatment for 30 minutes at the temperature of 200 ℃ in the air and 30 minutes at the temperature of 200 ℃ in a hydrogen-argon mixed gas to obtain the 1% Pt/Na-Mn catalyst.

Example 7

By usingPreparation of Pt-Na/Fe by co-impregnation method₂O₃A catalyst.

1.07mL of a 0.07M chloroplatinic acid aqueous solution and 10mL of a 4M NaOH solution were mixed uniformly, and the mixture was immersed in 1.2g of Fe₂O₃And (3) standing and aging for 12h after uniformly stirring on the carrier, and then drying for 12h in an oven at 80 ℃.

Treating the catalyst in hydrogen-argon mixed gas at 200 ℃ for 30min to obtain 1% Pt-Na/Fe₂O₃A catalyst.

Example 8

The monolithic Pt/Na-Fe/alumina honeycomb catalyst is prepared by a slurry coating method.

1.07mL of a 0.07M aqueous chloroplatinic acid solution, 14.0mL of a 1M ferric nitrate solution, and 1g of γ -Al₂O₃The powder is dissolved in 50mL of deionized water and stirred uniformly to obtain a mixed solution A. Uniformly dripping 212.3mL of 0.2M NaOH solution into the mixed solution A at the speed of 2mL/min under the condition of 80 ℃ water bath, adjusting the pH to 8.5 by using 1M HCl after finishing dripping, continuing stirring and crystallizing in the 80 ℃ water bath for 3 hours, and then standing and aging in the 80 ℃ water bath for 1 hour. The obtained precipitate is centrifugally washed until no chloride ion exists in the washing liquid, and then the precipitate is dried in an oven at 80 ℃ for 12 hours.

Weighing 2g of the catalyst powder, 20mg of surfactant (comprising 5mg of glycerol, 10mg of cellulose ether and 5mg of stearic acid) and 800mL of water, and ball-milling for 4 hours to prepare slurry. And (3) impregnating the cordierite honeycomb ceramic carrier into the coating slurry for 1h, drying at 80 ℃ for 12h, and finally treating at 200 ℃ for 30min in a hydrogen-argon mixed gas to obtain the integral Pt/Na-Fe/alumina honeycomb catalyst.

Comparative example 1

Preparation of Pt-Fe/gamma-Al by co-impregnation method₂O₃A catalyst.

1.07mL of a 0.07M chloroplatinic acid aqueous solution and 14.0mL of a 1M ferric nitrate solution were mixed uniformly and immersed in 1.2g of γ -Al₂O₃And (3) standing and aging for 12h after uniformly stirring on the carrier, and then drying for 12h in an oven at 80 ℃.

Treating the catalyst in hydrogen-argon mixed gas at a high temperature of 200 ℃ for 30min to obtain 1% Pt-Fe/gamma-Al₂O₃CatalysisAnd (3) preparing.

Comparative example 2

A magnetic stirrer, 5mL of NaOH/ethylene glycol solution (0.50mol/L) and 265 mu L of chloroplatinic acid/ethylene glycol solution (0.019mol/L) are added into a 50mL single-neck flask, the single-neck flask is fixed on an oil bath pot, a condenser pipe is installed, condensed water is introduced, 15min of Ar protective gas is introduced, and then the upper opening of the condenser pipe is sealed by a preservative film. The temperature of the oil bath pot is adjusted to 120 ℃, the stirring is started, and the stirring is carried out for 3 hours.

Taking out the single-neck flask from the oil bath pan for cooling, adjusting the temperature of the oil bath pan to 80 ℃, and weighing 0.1g of gamma-Al₂O₃Adding into a single-neck flask, placing the single-neck flask into the oil bath pot when the temperature of the oil bath pot is reduced to 80 ℃, opening and stirring, taking down a condenser tube, plugging the bottle mouth with a plug, adding 1M HCl solution into the single-neck flask by using an injector to adjust the pH to 9, then lifting the single-neck flask to be above the liquid level from the oil bath, and cooling to room temperature.

Centrifugally washing until no chloride ion exists in the washing liquid, then placing the washing liquid in a drying oven for drying for 12 hours at the temperature of 80 ℃, finally reducing for 30min at the temperature of 200 ℃ by using hydrogen-argon mixed gas as reducing gas to obtain 1% Pt/gamma-Al₂O₃A catalyst.

Comparative example 3

A260 ml Erlenmeyer flask was charged with a magnetic stirrer, 0.5g of Carbon Nanotubes (CNT), 110ml of concentrated nitric acid and 8ml of H₂And O, stirring uniformly, then slowly adding 96mL of concentrated sulfuric acid while stirring, stirring for 5min, and carrying out ultrasonic treatment for 5 min. Sealing with preservative film, ultrasonic treating at 60 deg.C for 2 hr, diluting with 2L water, washing CNT, filtering to neutrality, and drying in oven at 100 deg.C for 12 hr.

The obtained CNT is put into a tube furnace and roasted for 2h in an argon atmosphere at 1000 ℃ to obtain CNT-O. CNT-O is taken as a carrier, impregnation loading is carried out on the CNT-O by using chloroplatinic acid aqueous solution in an equal volume, aging is carried out for 12h under natural conditions after loading is finished, and drying is carried out for 12h at 100 ℃.

And reducing the mixed gas of hydrogen and argon as reducing gas at 200 ℃ for 30min to obtain the 1% Pt/CNT-O catalyst.

Comparative example 4

1.07mL of a 0.07M chloroplatinic acid aqueous solution was dissolved in 14.0mL of a 1M ferric nitrate solution, and the mixture was stirred uniformly to obtain a mixed solution A. Under the condition of 80 ℃ water bath, uniformly dripping the mixed solution A) into 100mL of 0.2M NaOH solution at the speed of 2mL/min, adjusting the pH to 8.5 by using 1M HCl after finishing dripping, continuing stirring and crystallizing in 80 ℃ water bath for 3h, and then standing and aging in 80 ℃ water bath for 1 h.

And centrifugally washing the obtained precipitate until no chloride ion exists in the washing liquid, then placing the precipitate in a drying oven for drying at the temperature of 80 ℃ for 12 hours, and finally carrying out high-temperature treatment in a hydrogen-argon mixed gas at the temperature of 200 ℃ for 30min to obtain the 1% Pt/Na-Fe-4 catalyst.

The contents of the raw material gases in the following experimental examples 1 to 3 are volume contents.

Experimental example 1

Evaluation conditions of the catalyst: the reaction pressure is normal pressure, and the raw material gas for reaction is 85% CO₂+14.6％He+0.1％CO+0.3％H₂(80mL/min) and air (5mL/min), the catalyst loading volume is 1mL, and the space velocity is 5000h^-1. The CO catalytic oxidation conversion rate of the catalyst reaches the minimum reaction temperature T of 90 percent and 99 percent respectively₉₀And T₉₉See table 1.

TABLE 1 results of examples and comparative examples

The catalytic stability of the catalyst product 1% Pt/Na-Fe-1 obtained in example 3 was tested, and as shown in FIG. 1, the catalyst maintained stable catalytic performance and the CO conversion rate was substantially maintained at about 99% within 20 hours.

Experimental example 2

Evaluation conditions of the catalyst: the reaction pressure is normal pressure, and the raw material gas for reaction is 85% CO₂+14.6％He+0.1％CO+0.3％H₂(80mL/min), air (5mL/min) and 100ppm H₂S gas (3.5mL/min), catalyst loading volume of 1mL, space velocity of 5000h^-1. CO catalytic oxidation of catalystThe conversion rate reaches 90 percent and 99 percent respectively₉₀And T₉₉See table 2, where the results with the designation "-" indicate that the catalyst activity did not achieve this conversion.

TABLE 2 results of examples and comparative examples

Experimental example 3

Evaluation conditions of the catalyst: the reaction pressure is normal pressure, and the reaction raw material gas is 49% H₂+ 50% He + 1% CO (80mL/min) and air (2mL/min), a catalyst loading volume of 1mL, and a space velocity of 5000h^-1. The CO catalytic oxidation conversion rate of the catalyst reaches the minimum reaction temperature T of 90 percent and 99 percent respectively₉₀And T₉₉See table 3, wherein the results with the designation "-" indicate that the catalyst activity did not achieve this conversion.

TABLE 3 results of examples and comparative examples

Catalyst and process for preparing same	T₉₀(℃)	T₉₉(℃)
			Example 1	45	50
Example 2	45	55
			Example 3	40	50
Example 4	60	105
			Example 5	35	40
Example 6	75	100
			Example 7	135	160
Example 8	65	90
			Comparative example 1	-	-
Comparative example 2	145	180
			Comparative example 3	100	130

Claims

1. a catalyst for CO oxidation, comprising: with Pt element as active component, transition metal element M2 oxide and alkali metal element M1, M2 is selected from one or more of Mn, Mo, Fe, Ni elements, M1 It is an alkali metal element, wherein the Pt element accounts for 0.1-2 wt % of the total mass of the catalyst, and the M1 element accounts for 1-10 wt % of the total catalyst mass.

2. The catalyst according to claim 1, characterized in that, M2 is selected from one or more of Mn, Fe and Ni elements, and the mass of Pt is 0.15-3% of the mass of M2 oxide.

3. catalyzer according to claim 1, is characterized in that, transition metal element M is Mn element;

Preferably, M1 is selected from Na and/or K elements.

4. a preparation method of the catalyst of CO oxidation described in any one of claim 1-3, adopts co-precipitation method to prepare;

Preferably, it includes: mixing the Pt precursor solution and the M2 precursor solution to obtain a mixed solution A, adding the mixed solution A dropwise to the alkaline solution containing the M1 element, and adjusting pH=7-10 after the dropwise addition to obtain a mixture B , the mixture B is crystallized, washed, and treated at high temperature to obtain a catalyst.

5. preparation method according to claim 4 is characterized in that, the amount of material of M1 element in the solution of M1 element and the amount of material of Pt in the Pt precursor solution and the amount of material of M2 in the M2 precursor solution The amount of material The ratio of the sum of the two is 2:1 to 4:1.

6. The preparation method according to claim 4 or 5, wherein the high temperature treatment is to heat at a temperature of 150-400°C;

Preferably, the high temperature treatment process is carried out in an air atmosphere or in a mixed gas containing hydrogen;

More preferably, the high temperature treatment is first performed in an air atmosphere, and then performed in a hydrogen-containing mixed gas.

7. The preparation method according to claim 4 or 5, wherein the high temperature treatment is heating at a temperature of 150-250°C;

8. The preparation method according to any one of claims 4-7, wherein a drying step is performed before the high temperature treatment, and the drying temperature is lower than 100°C;

Preferably, the drying temperature is 70-100°C.

9. The preparation method according to any one of claims 4-8, wherein the Pt precursor is a water-soluble platinum element-containing salt solution; preferably, it includes chloroplatinic acid or platinum chloride;

M2 precursor is a water-soluble salt solution containing M2 element; preferably nitrate or chloride containing M2 element;

The solution containing M1 element includes M1OH or M1 ₂ CO ₃ ; preferably, the concentration of the solution of M1 element is 0.1-0.5M.

10. a preparation method of the catalyst of the CO oxidation of any one of claims 1-3, comprising:

Mix the Pt precursor solution, the M2 precursor solution and the alumina powder to obtain a mixed solution A1, and mix the solution containing the M1 element with the mixed solution A1, and then adjust the pH=7 to 10 to obtain a mixture B1. The mixture B1 is crystallized, Wash and dry to obtain catalyst powder,

The obtained catalyst powder, surfactant and water are mixed to form a catalyst slurry, and the ceramic carrier with pores is mixed with the catalyst slurry to obtain a mixture C1, and the mixture C1 is treated at a high temperature to obtain a coated catalyst;

Preferably, the mass of the Pt element is 0.5-2% of the mass of the alumina.